Although the entire novel tells of only one day, Virginia Woolf covers a lifetime in her enlightening novel of the mystery of the human personality. The delicate Clarissa Dalloway, a disciplined English lady, provides the perfect contrast to Septimus Warren Smith, an insane ex-soldier living in chaos. The reader also learns of Clarissa Dalloway through the thoughts of other characters, such as her old passion Peter Walsh, her husband Richard, and her daughter Elizabeth. Septimus Warren Smith, driven insane by witnessing the death of his friend in the war, acts as Clarissa's societal antithesis, but the reader learns that they often are more similar than different. Virginia Woolf examines the human personality in two distinct methods: she observes that different aspects of one's personality emerge in front of different people, and she analyzes how the appearance of a person and the reality of that person diverge. By offering the personality in all its varying forms, Woolf demonstrates the compound nature of human beings.

Although no one else in this novel relates in any way to the lunacy of Septimus Warren Smith, Woolf finds a way to verify the intricacy of his personality. Unlike Sally, Richard, and Peter, whose personality changes are exposed through comparison and contrast with other characters, Septimus's complex character reveals itself when Woolf analyzes the appearance of Septimus Smith versus his reality. On the surface, as he appears to the world, Septimus is a maniac who speaks to thin air and converses with his dead friend from the war, Evans. Even when Woolf narrates Septimus's thoughts, the reader beholds the sad beauty of his psychotic world. Time, setting, and circumstance are all distorted. So, in appearance, this man acts as the complete opposite of Clarissa Dalloway, and so it is ironic that in reality, Septimus, a lunatic, and Clarissa, a cultured lady, are more similar than anyone else in the novel. Both value the possession and privacy of their souls more than anything else: Mrs. Dalloway attempts to keep her most serious thoughts, hopes, and reflections to herself, because no one else would treasure them as she does. Similarly, but in a more intense manner, Septimus wishes to keep his soul, his essence which makes him an individual, to himself. Just as Miss Kilman, Elizabeth's controlling tutor, frightens Clarissa, Septimus feels that his doctors invade the privacy of his soul by demanding too much of him. Just as Clarissa feels that Miss Kilman hates her and fancies her soul, Septimus, in his insane way, believes that Dr. Holmes and Dr. Bradshaw wish to invade his most private depths. Septimus even describes Holmes as having red nostrils and as "snuffing into every secret place." So Clarissa and Septimus are complete opposites in terms of appearance to society, but in reality, on the psychological level, both toil to preserve their privacy. For this reason, and this reason alone, Clarissa marries Richard over Peter; she is afraid of the emotional intimacy Peter expects. Likewise, Septimus takes his own life before the doctors can carry him away from his wife and from his world. In his derisive last words, "I'll give it to you," when Dr. Holmes intends to drag him off, Septimus gives his physical body to the confounded doctor, but through death, refuses to part with his soul.